Some people may be aware of DeCSS, a bit of C of which the MPAA (and the rest of the US gov't) are not very fond because it decrypts copy- and read-protected DVDs for playing on, say, linux machines where no such license is available.

I had the idea for a challenge along the lines of "write the shortest DeCSS-er or brute-forcer" but before properly writing up a challenge for the sandbox, it occurred to me that perhaps the community would not take kindly to the posting of a challenge which may or may not break a law (not really) or probably enrage a lawyer somewhere.

Can I propose such a challenge?

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    \$\begingroup\$ I'm not a mod on this site. Having said that, I know SE generally does its best to avoid having anything illegal on its sites. DeCSS can certainly be obtained elsewhere, but there's no good reason to make here one of those places. Certainly no reason good enough to outweigh the potential (or likely) problems. Thank you for asking first. :) \$\endgroup\$ – El'endia Starman Nov 20 '15 at 2:54
  • \$\begingroup\$ The flag of france can also be obtained elsewhere, but the game was to generate it in a short way for fun as is the point in this prospective challenge: not to make DeCSS more available but to golf a cool decryption algorithm. \$\endgroup\$ – cat Nov 20 '15 at 2:55
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    \$\begingroup\$ The flag of France isn't illegal at all! There have been legal threats against sites that hosted DeCSS (in ~2000, but still). It'd be good to not include SE in that list. Now, decryption in general should be fine, I think. \$\endgroup\$ – El'endia Starman Nov 20 '15 at 2:58
  • \$\begingroup\$ "decryption in general should be fine, I think" yes, as long as the UK government don't have anything to say about it ;) \$\endgroup\$ – cat Nov 20 '15 at 3:03
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    \$\begingroup\$ It's worth noting that this is reminiscent of this deleted challenge, which was... not particularly well received. When in doubt, I'd advise against challenges related to anything that could potentially involve legal issues. \$\endgroup\$ – Doorknob Nov 20 '15 at 3:03

I have considered posting DeCSS as a challenge, and it may even be on one of my Trello boards; the biggest obstacle I see is writing a really good test suite without infringing copyright. I don't see the code itself as an obstacle: the legal protection claimed was trade secret, but the plaintiffs stupidly published the code in their complaint, so legally it's no longer a secret.



Like the comments mentioned, DeCSS's legality is somewhere between questionable and illegal, depending on who you ask and which laws you look at. To err on the side of safety, let's not have the code posted on a Stack Exchange network site. We like being able to do code golf here, and if the MPAA were to decide to take legal action, there's a possibility that we wouldn't be able to have this site anymore. Though it's been several years since the last legal challenge, we don't want to take any chances.

Any content of questionable legality should not be posted on any Stack Exchange site.

  • \$\begingroup\$ Even if the MPAA were to take action, it would most likely be in the form of a DMCA takedown request. Since the code would be contributed by third parties (not the site hosts themselves), there would be no reason to close the site, simply deleting the post would be sufficient. I'm not saying it's a great idea to post it, but saying the site will be shut down over it is a bit "the sky is falling" IMO. \$\endgroup\$ – Geobits Nov 20 '15 at 13:34
  • \$\begingroup\$ @Geobits I'm talking worst-case here. The more likely case is a DMCA takedown, yes, which probably wouldn't make the admins very happy with us, either. \$\endgroup\$ – user45941 Nov 20 '15 at 22:44
  • \$\begingroup\$ There was once a legal challenge for PPCG? \$\endgroup\$ – Justin Nov 28 '15 at 7:12
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    \$\begingroup\$ @Justin Legal challenge against DeCSS, not PPCG/SE/SO. \$\endgroup\$ – user45941 Nov 28 '15 at 7:43

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